Contact type magnetic disc apparatus

ABSTRACT

The density of the magnetic head protective layer is set to be higher than the density of a magnetic disc medium protective layer. Also, the Young&#39;s modulus of the magnetic head protective layer is set to be higher than the Young&#39;s modulus of the magnetic disc medium protective layer. Furthermore, the thickness of the magnetic disc medium protective layer is set to be between 1 and 10 nm, and the hardness of the magnetic head protective layer is set to be between 1.5 and 2.0 times the hardness of the magnetic disc medium protective layer. It is thus possible to provide a highly reliable magnetic disc apparatus.

The present application is a Divisional application of U.S. patentapplication Ser. No. 09/328,449, filed on Jun. 9, 1999, now U.S. Pat.Ser. No. 6,385,013.

BACKGROUND OF THE INVENTION

The present invention relates to contact type magnetic disc apparatusesand, more particularly, to contact type magnetic disc apparatuses, inwhich a magnetic head is driven on frictional contact with a magneticdisc medium for recording and reproduction.

Recently, in data storage file fields, the recording density is beingsteadily improved. For increasing the recording density of the magneticdisc apparatus, it is thus one of the most important factors to reducethe gap between a magnetic head for writing and reading data and amagnetic disc medium storing the data. For reducing the gap between themagnetic head and the magnetic disc medium, a so-called contact typemagnetic disc apparatus, in which the magnetic head is driven infrictional contact with the magnetic disc medium surface for recordingand reproduction, has been developed (See, for instance H. Hamilton,Journal of Magnetic Society of Japan, Vol. 15, Supplement No. S2 (1991)483, and also Japanese Patent Application No. 5-508808 (Japanese PatentPublication Disclosure No. 5-814495). In such contact type magnetic discapparatuses, it is important to prevent wear and damages of the magneticdisc medium and the magnetic head.

Various techniques have been developed for the purpose of reducing thewear and damages in the contact type magnetic disc apparatus. Forinstance, Japanese Patent Laid-Open No. 2-249177 discloses a techniquefor preventing the wear of the magnetic disc medium and the magnetichead in such a manner that surplus liquid lubricant is always suppliedto the magnetic disc medium surface by circulating the lubricant in themagnetic disc apparatus. Also, Japanese Patent Laid-Open No. 4-113568discloses a technique, in which non-newton liquid lubricant is providedbetween the magnetic head and the magnetic disc medium in the samestructure as above. Furthermore, Japanese Patent Laid-Open No. 5-1511735discloses a slider structure which is suited for sliding over lubricanton the magnetic disc medium surface.

In the meantime, recent high recording density magnetic disc apparatusesmostly employ a separate recording and recording element type magnetichead, which uses an MR reproducing element utilizing magnetoresitive(MR) effect for reproducing data (hereinunder referred to as MR head).The MR head usually has a protective layer formed on the slider surfacefor the purposes of preventing the electric discharge of the element andimproving the corrosion resistance thereof, as disclosed in, forinstance, Japanese Patent Disclosure No. 4-364217. The wear of theprotective layer of the head leads to deterioration of the MR headcharacteristics, and in the magnetic disc apparatus employing the MRelement it is thus particularly important to suppress wear and damagesof the head side protective layer. To this end, Japanese PatentLaid-Open No. 9-204626 discloses a magnetic disc apparatus having aprotective layer on the sliding surface of the magnetic head, in whichthe hardness of the protective layer is set to be higher than two times,Preferably three times, the hardness of a protective layer of themagnetic disc medium for preventing wear and damages of both themagnetic disc medium protective layer and the magnetic head protectivelayer.

The prior art magnetic disc apparatuses as shown above, however, havethe following problems.

The magnetic disc apparatuses using liquid lubricant, as disclosed inthe Japanese Patent Laid-Open No. 2-249177, 4-113568 and 5-151735, it issought to suppress wear by always supplying surplus lubricant to thefrictional surfaces of the magnetic head and the magnetic disc medium.However, the actual magnetic disc apparatus has a problem that it isextremely difficult to steadily supply clean lubricant at a constantrate so that it is difficult to ensure stable operation of the apparatusfor long time.

The technique of providing protective layers on the sliding surface ofthe magnetic head and providing a protective layer on the magnetic discmedium as disclosed in the Japanese Patent Disclosure No. 9-204626, iseffective so long as the magnetic disc medium protective layer has aslarge thickness as 15 nm or above. However, where the thickness of theprotective layer is reduced to 10 nm or below, the magnetic disc mediumprotective layer may be worn and damaged, resulting in wear of themagnetic head protective layer. Particularly, since it is nowadaysimportant to reduce the magnetic spacing to cope with a recentincreasing recording density trend, it is important to reduce thethickness of the protective layer and layer.

SUMMARY OF THE INVENTION

In view of the above prior art, an object of the present inventionconcerns a magnetic disc medium, which permits recording andreproduction in a state that it can be in intermittent or continuouscontact with a magnetic head, and it is sought to prevent wear anddamages of a magnetic head protective layer and a magnetic discprotective layer in contact with each other, particularly it is soughtto provide a magnetic disc apparatus, which is less subject to wear ordamages even when the thicknesses of the magnetic head protective layerand the magnetic disc medium protective layer are reduced, as well ashaving high recording density and being excellently reliable.

According to an aspect of the present invention, there is provided amagnetic disc apparatus comprising a magnetic disc medium having aprotective layer on the surface, a means for rotating the magnetic discmedium, a magnetic head for recording and reproducing data on and fromthe magnetic disc medium, and a control means for controlling themagnetic disc medium, the rotating means and the head, the head beingrotated intermittently or continuously in frictional contact with themagnetic disc medium, wherein the head has a protective layer formed onat least part of a portion to be in frictional contact with the magneticdisc medium, the magnetic head protective layer having a density higherthan the density of the magnetic disc medium protective layer.

With these settings, wear and damages due to the sliding are not causedpartially on either the magnetic disc medium protective layer side orthe magnetic head protective layer side, but they can proceed uniformlyon both sides. Consequently, the degree of wear and damages can beextremely reduced. It is thus possible to provide a highly reliablemagnetic disc apparatus, which is subject to less wear and damages andexcellently reliable.

According to another aspect of the present invention, there is provideda magnetic disc apparatus comprising a magnetic disc medium having aprotective layer on the surface, a means for rotating the magnetic discmedium, a magnetic head for recording and reproducing data on and fromthe magnetic disc medium, and a control means for controlling themagnetic disc medium, the rotating means and the head, the head beingrotated intermittently or continuously in frictional contact with themagnetic disc medium, wherein the magnetic head protective layer has aYoung's modulus higher than the Young's modulus of the magnetic discmedium protective layer.

According to other aspect of the present invention, there is provided amagnetic disc apparatus comprising a magnetic disc medium having aprotective layer of thickness between 1 and 10 nm on the surface, ameans for rotating the magnetic disc medium, a magnetic head forrecording and reproducing data on and from the magnetic disc medium, anda control means for controlling the magnetic disc medium, the rotatingmeans and the head, wherein the head has a protective layer formed on atleast part of a portion to be in frictional contact with the magneticdisc medium, the magnetic head protective layer of a hardness between1.5 and 2.0 times the hardness of the magnetic disc medium protectivelayer.

The magnetic head protective layer and the magnetic disc mediumprotective layer are made of the same material. The magnetic headprotective layer and the magnetic disc medium protective layer are madeof material including mainly carbon.

According to still other aspect of the present invention, there isprovided a magnetic disc apparatus comprising a magnetic disc mediumhaving a protective layer on its surface, and a magnetic head forrecording and reproducing data on and from the magnetic disc mediumhaving a protective layer on its surface, the magnetic disc medium andthe magnetic head being rotated in frictional contact therebetween,wherein the magnetic head protective layer having a density higher thanthe density of the magnetic disc medium protective layer.

According to further aspect of the present invention, there is provideda magnetic disc apparatus comprising a magnetic disc medium having aprotective layer on its surface, and a magnetic head for recording andreproducing data on and from the magnetic disc medium having aprotective layer on its surface, the magnetic disc medium and themagnetic head being rotated in frictional contact therebetween, whereinthe magnetic head protective layer has a Young's modulus higher than theYoung's modulus of the magnetic disc medium protective layer.

According to still further aspect of the present invention, there isprovided a magnetic disc apparatus comprising a magnetic disc mediumhaving a protective layer on its surface, and a magnetic head forrecording and reproducing data on and from the magnetic disc mediumhaving a protective layer on its surface, the magnetic disc medium andthe magnetic head being rotated in frictional contact therebetween,wherein the magnetic head protective layer of a hardness between 1.5 and2.0 times the hardness of the magnetic disc medium protective layer.

The densities of the magnetic disc medium protective layer and themagnetic bead protective layer are set to be in ranges of 1.2 to 1.8(g/cm³) and 1.0 to 2.0 (g/cm³), respectively. The Young's moduluses ofthe magnetic disc medium protective layer and the magnetic headprotective layer are set to be in ranges of 200 to 400 (GPa) and 250 to500 (GPa), respectively. The thickness of the magnetic disc mediumprotective layer is set to be between 1 and 10 nm, and the hardness ofthe magnetic head protective layer is set to be between 1.5 and 2.0times the hardness of the magnetic disc medium protective layer. Thethickness of the magnetic disc medium protective layer is 15 nm orabove, and the hardness of the magnetic head protective layer is higherthan 2.0 times the hardness of the magnetic disc medium protectivelayer. The magnetic head protective layer and the magnetic disc mediumprotective layer are formed as a carbon layer with or without a hydrogenor nitrogen content. The magnetic head protective layer and the magneticdisc medium protective layer are formed as SiC, SiN or BN.

Other objects and features will be clarified from the followingdescription with reference to attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the basic structure of the magneticdisc apparatus according to the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

Preferred embodiments of the present invention will now be describedwith reference to the drawings.

FIG. 1 is a sectional view showing the basic structure of the magneticdisc apparatus according to the present invention. Reference numeral 14designates a magnetic disc medium, which is a laminate having asubstrate 10, a base layer 11, a magnetic layer 12, a magnetic discmedium protective layer 13 and a lubricant layer 15, these layers beinglaminated in the mentioned order. The medium 14 is mounted on androtated by a spindle motor 16. A magnetic head, on the other hand, has amagnetic head slider 20 a magnetic recording/reproducing element 17, acontact pad 19 and a magnetic head protective layer 18, and it issupported by a support arm 24 via a gimbal spring 22 and a load beamspring 23.

Using a magnetic disc apparatus having the construction as describedabove, relations of the physical properties and the mechanicaldurability of the magnetic disc protective layer and the magnetic headprotective layer to one another were investigated. As a specificexample, the investigations were conducted as follows.

Of the magnetic disc medium 14 in the embodiment shown in FIG. 1, as thesubstrate 10 was used a glass substrate having a diameter of 63.5 mm anda thickness of 0.3 mm. On this glass substrate, the base layer 11 andthe magnetic layer 12 were formed by sputtering Cr and CoCrTaPt tothicknesses of 100 nm and 30 nm, respectively. Then the magnetic discmedium protective layer 13 was formed as a carbon layer with or withouta hydrogen or nitrogen content either by a plasma chemical vapordeposition (CVD) method or a sputtering method. Finally, the lubricantlayer 15 was formed from perfluoropolyether to a thickness of 5 nm by adipping method.

The magnetic head slider 20 was formed from Al₂O₃—TiC such as to have awidth of 1 mm, a length of 1.2 mm and a thickness of 0.3 mm. The contactpad 19 was formed such as to have a diameter of 30 μm and a height of 6μm by milling the magnetic head slider 20 with argon ions.

As the magnetic recording/reproducing element 17 an MR reproducingelement of NiMn was used. The magnetic head protective film 18 wasformed on the magnetic recording/reproducing element 17 and the contactpad 19 on the side of these parts facing the magnetic disc medium 14.The magnetic head protective layer 18 was formed by sputtering siliconto form a close contact layer 1 nm in thickness and then forming acarbon layer with or without a hydrogen or nitrogen content by theplasma CVD method or the sputtering method. The thickness of themagnetic head protective layer 18 was varied in a range of 2 to 20 nm astotal thickness of the silicon and carbon layers.

The gimbal spring 22, the load beam spring 23 and the support arm 24supporting the magnetic head slider 20 were all formed from stainlesssteel. The gimbal spring 22 was formed to have a length of 2 mm, a widthof 1 mm and a thickness of 0.01 mm. The load beam spring 23 was formedto have a length of 10 mm, a width of 1.2 mm and a thickness of 0.05 mm.The support arm 24 was formed to have a length of 15 mm, a width of 3 mmand a thickness of 1 mm. A pivot 21 was formed by compressing the loadbeam spring 23 such as to be a spherical projection having a diameter of0.2 mm and a height of 0.1 m.

The physical properties of the magnetic head protective layer and themagnetic disc medium protective layer were controlled by varying thekind and flow rate of the CVD gas and sputtering gas and also the inputpower level and the bias voltage level when forming the layer and thelayer. Protective layers and layers having predetermined densities,Young's moduluses and hardnesses were thus formed, thus producingExamples No. 1 to 4 of magnetic disc apparatus. Contrast Examples No. 1to 87 were also formed for comparison with the examples.

Durability tests were then conducted on the magnetic disc apparatusesthus produced. In the tests, the magnetic disc medium was held rotatingat 5,400 r.p.m. in frictional contact with the magnetic head slider at aradial position of 30 mm for 1,000 hours, and then the wear heights ofthe magnetic head protective layer and the magnetic disc protectivelayer were measured by using an inter-atomic power microscope and anellipsometer.

Tables 1 to 4 show the wear heights of the magnetic disc mediumprotective layers and an the magnetic head protective layers obtained asthe results of the durability tests conducted by using magnetic discapparartuses, which were producing by setting the densities of themagnetic disc medium protective layer and the magnetic head protectivelayer in ranges of 1.2 to 1.8 (g/cm³) and 1.0 to 2.0 (g/cm³),respectively. The thicknesses of the magnetic disc medium protectivelayer and the magnetic head protective layer were both set to 10 nm.

With reference to the results of tests on Examples No. 1 to 20 andContrast Examples No. 1 to 24 in Tables 1 to 4, it will be seen that thewear heights of the magnetic disc medium protective layer and themagnetic head protective layer can both be held to be small when thedensity of the magnetic head protective layer is higher than that of themagnetic disc medium protective layer. It will also be seen that whenthe density of the magnetic head protective layer is equal to or lowerthan the density of the magnetic disc medium protective layer, the wearheight of the magnetic head protective layer is extremely large,although the wear height of the magnetic disc medium protective layercan be held to be small. It can thus be concluded that by setting thedensity of the magnetic head protective layer to be higher than thedensity of the magnetic disc medium protective layer, it is possible toextremely reduce the wear of both the magnetic disc medium protectivelayer and the magnetic head protective layer and provide a magnetic discapparatus which is less subject to wear and damages, excellently durableand highly reliable.

Tables 5 and 6 show the results of durability tests, i.e., wear heightsof magnetic disc medium protective layers and magnetic heads protectivelayers, obtained with magnetic disc apparatuses, which were produced bysetting the Young's moduluses of the magnetic disc medium protectivelayer and the magnetic head protective layer in ranges of 200 to 400(GPa) and 150 to 500 (GPa), respectively. The thicknesses of themagnetic disc medium protective layer and the magnetic head protectivelayer were both set to 10 nm.

With reference to the results of tests on Examples No. 21 to 32 andContrast Examples No. 25 to 36 in Tables 5 and 6, it will be seen thatthe wear heights of the magnetic disc medium protective layer and themagnetic head protective layer can both be held to be small when theYoung's modulus of the magnetic head protective layer is higher than theYoung's modulus of the magnetic disc medium protective layer. It willalso be seen that when the Young's modulus of the magnetic headprotective layer is equal to or lower than the Young's modulus of themagnetic disc medium protective layer, the wear height of the magnetichead protective layer is extremely large although the wear height of themagnetic disc medium protective layer can be held to be small. It canthus be concluded that by setting the Young's modulus of the magnetichead protective layer to be higher than the Young's modulus of themagnetic disc medium protective layer, it is possible to extremelyreduce the wears of both the magnetic disc medium protective layer andthe magnetic head protective layer and provide a magnetic discapparatus, which is less subject to wear and damages, excellentlydurable and highly reliable.

Tables 7 to 11 show the results of durability tests, i.e., wear heightsof magnetic disc medium protective layers and magnetic head protectivelayers, obtained with magnetic disc apparatuses which were produced bysetting the hardnesses of the magnetic disc medium protective layer andthe magnetic head protective layer to be 40 (GPa) and in a range of 40to 140 (GPa), respectively, with thicknesses of the magnetic disc mediumprotective layer in a range of 1 to 20 nm. The thickness of the magnetichead protective layer was set to be 10 nm.

With reference to the results of tests conducted on Examples No. 33 to41 and Contrast Examples 37 to 63 in Tables 7 to 9, it will be seen thatso long as the thickness of the magnetic disc medium protective layer isbetween 1 and 10 nm, the wear heights of the magnetic disc mediumprotective layer and the magnetic head protective layer can both be heldto be small when the hardness of the magnetic head protective layer isbetween 1.5 and 2.0 times the hardness of the magnetic disc mediumprotective layer. It will also be seen that when the hardness of themagnetic head protective layer is not higher than 1.5 times the hardnessof the magnetic disc medium protective layer, the wear height of themagnetic head protective layer is large. It will further be seen thatwhen the hardness of the former is higher than 2.0 times the hardness ofthe latter, the wear heights of the magnetic disc medium protectivelayer and the magnetic head protective layer are both extremely large.

With reference to the results of tests conducted on Contrast ExamplesNo. 64 to 87 in Tables 10 and 11, so long as the thickness of themagnetic disc medium protective layer is 15 nm or above, the wearheights of the magnetic disc medium protective layer and the magnetichead protective layer can both be held to be small when the hardness ofthe magnetic head protective layer is higher than 2.0 times the hardnessof the magnetic disc medium protective layer. It will also be seen thatwhen the hardness of the magnetic head protective layer is not higherthan 2.0 times the hardness of the magnetic disc medium, the wear heightof the magnetic head protective layer is extremely large although thewear height of the magnetic disc medium protective layer can be held tobe small. It can thus be concluded that it is possible to extremelyreduce the wears of the magnetic disc medium protective layer and themagnetic head protective layer and provide a magnetic disc apparatus,which is less subject to wear and damages, excellently durable andhighly reliable, by setting the hardness of the magnetic headsprotective layer to be between 1.5 and 2.0 times the hardness of themagnetic disc medium protective layer when the thickness of the magneticdisc medium protective layer is between 1 and 10 nm, and to be higherthan 2.0 times the hardness of the magnetic disc medium protective layerwhen the magnetic disc medium protective layer is as thick as 15 nm.

Tables 7 to 11 show the results of tests conducted by setting constantmagnetic head protective layer thickness of 10 nm. When the magnetichead protective layer thickness was varied in a range of 2 to 20 nm, thewears of the magnetic disc medium protective layer and the magneticheads protective layer were hardly changed.

While in the above examples the magnetic head protective layer and themagnetic disc medium protective layer were formed as a carbon layer withor without a hydrogen or nitrogen content, the same results could beobtained by using SiC, SiN and BN.

The materials and the method of formation of the substrate, the baselayer, the magnetic layer, the magnetic disc medium protective layer,the magnetic head protective layer, the lubricant layer, the magnetichead slider, the magnetic recording/reproducing element, the gimbalspring, the load beam spring, the supporting arm, and the contact pad inthe above examples are by no means limitative, and it is possible to usewell-known materials and methods of formation without any speciallimitation.

While in the above examples a lubricant was used for the magnetic discmedium protective layer, it is possible to obtain the same effects asthose described in connection with the examples without any lubricant.

As has been described in the foregoing, according to the invention thefollowing effects are obtainable.

By setting the Young's modulus or the density of the magnetic headprotective layer to be higher than the Young's modulus or the density ofthe magnetic disc medium protective layer, or in the case where themagnetic disc medium protective layer has as small thickness as 1 to 10nm by setting the hardness of the magnetic head protective layer to bebetween 1.5 to 2.0 times the magnetic disc medium protective layer, wearand damages due to the sliding are not caused partially on either themagnetic disc medium protective layer side or the magnetic headprotective layer side, but they can proceed uniformly on both sides. Itis thus possible to reduce the degree of wear and damages and provide ahighly reliable magnetic disc apparatus, which is subject to less wearand damages and excellently reliable.

Changes in construction will occur to those skilled in the art andvarious apparently different modifications and embodiments may be madewithout departing from the scope of the present invention. The matterset forth in the foregoing description and accompanying drawings isoffered by way of illustration only. It is therefore intended that theforegoing description be regarded as illustrative rather than limiting.

TABLE 1 RELATIONSHIP BETWEEN DENSITIES OF MAGNETIC DISC MEDIUMPROTECTIVE LAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHTWEAR HEIGHT OF WEAR THICKNESS THICKNESS DENSITY OF DENSITY OF MAGNETICHEIGHT OF OF DISC OF MAGNETIC MAGNETIC DISC MAGNETIC MAGNETIC MAGNETICDISC MEDIUM HEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVE PROTECTIVEPROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE LAYER LAYER LAYER LAYERLAYER LAYER NO. (g/cm³) (g/cm³) (nm) (nm) (nm) (nm) CONTRAST 1.2 1.0 0.48.6 10 10 EXAMPLE 1 CONTRAST 1.2 1.1 0.6 7.4 10 10 EXAMPLE 2 CONTRAST1.2 1.2 1.2 6.9 10 10 EXAMPLE 3 EXAMPLE 1 1.2 1.3 1.4 1.8 10 10 EXAMPLE2 1.2 1.4 1.5 1.6 10 10 EXAMPLE 3 1.2 1.5 1.4 1.7 10 10 EXAMPLE 4 1.21.6 1.6 1.0 10 10 EXAMPLE 5 1.2 1.7 1.8 1.2 10 10 EXAMPLE 6 1.2 1.8 1.91.6 10 10 EXAMPLE 7 1.2 1.9 1.8 1.0 10 10 EXAMPLE 8 1.2 2.0 1.9 0.6 1010

TABLE 2 RELATIONSHIP BETWEEN DENSITIES OF MAGNETIC DISC MEDIUMPROTECTIVE LAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHTWEAR THICKNESS HEIGHT OF WEAR OF THICKNESS DENSITY OF DENSITY OFMAGNETIC HEIGHT OF MAGNETIC OF MAGNETIC MAGNETIC DISC MAGNETIC DISCMAGNETIC DISC MEDIUM HEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVE PROTECTIVEPROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE LAYER LAYER LAYER LAYERLAYER LAYER NO. (g/cm³) (g/cm³) (nm) (nm) (nm) (nm) CONTRAST 1.4 1.0 0.38.7 10 10 EXAMPLE 4 CONTRAST 1.4 1.1 0.4 8.5 10 10 EXAMPLE 5 CONTRAST1.4 1.2 0.5 7.5 10 10 EXAMPLE 6 CONTRAST 1.4 1.3 1.2 8.1 10 10 EXAMPLE 7CONTRAST 1.4 1.4 1.5 6.2 10 10 EXAMPLE 8 EXAMPLE 9 1.4 1.5 1.6 1.3 10 10EXAMPLE 10 1.4 1.6 1.4 1.2 10 10 EXAMPLE 11 1.4 1.7 1.7 1.4 10 10EXAMPLE 12 1.4 1.8 1.6 1.6 10 10 EXAMPLE 13 1.4 1.9 1.3 1.0 10 10EXAMPLE 14 1.4 2.0 1.9 0.8 10 10

TABLE 3 RELATIONSHIP BETWEEN DENSITIES OF MAGNETIC DISC MEDIUMPROTECTIVE LAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHTWEAR THICKNESS HEIGHT OF WEAR OF THICKNESS DENSITY OF DENSITY OFMAGNETIC HEIGHT OF MAGNETIC OF MAGNETIC MAGNETIC DISC MAGNETIC DISCMAGNETIC DISC MEDIUM HEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVE PROTECTIVEPROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE LAYER LAYER LAYER LAYERLAYER LAYER NO. (g/cm³) (g/cm³) (nm) (nm) (nm) (nm) CONTRAST 1.6 1.0 0.49.3 10 10 EXAMPLE 9 CONTRAST 1.6 1.1 0.5 9.1 10 10 EXAMPLE 10 CONTRAST1.6 1.2 0.4 8.6 10 10 EXAMPLE 11 CONTRAST 1.6 1.3 0.9 8.9 10 10 EXAMPLE12 CONTRAST 1.6 1.4 1.1 7.9 10 10 EXAMPLE 13 CONTRAST 1.6 1.5 1.3 8.1 1010 EXAMPLE 14 CONTRAST 1.6 1.6 1.5 7.5 10 10 EXAMPLE 15 EXAMPLE 15 1.61.7 1.8 1.6 10 10 EXAMPLE 16 1.5 1.8 1.9 1.3 10 10 EXAMPLE 17 1.6 1.91.6 1.2 10 10 EXAMPLE 18 1.6 2.0 1.8 1.1 10 10

TABLE 4 RELATIONSHIP BETWEEN DENSITIES OF MAGNETIC DISC MEDIUMPROTECTIVE LAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHTWEAR THICKNESS HEIGHT OF WEAR OF THICKNESS DENSITY OF DENSITY OFMAGNETIC HEIGHT OF MAGNETIC OF MAGNETIC MAGNETIC DISC MAGNETIC DISCMAGNETIC DISC MEDIUM HEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVE PROTECTIVEPROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE LAYER LAYER LAYER LAYERLAYER LAYER NO. (g/cm³) (g/cm³) (nm) (nm) (nm) (nm) CONTRAST 1.8 1.0 0.69.3 10 10 EXAMPLE 16 CONTRAST 1.8 1.1 0.5 9.7 10 10 EXAMPLE 17 CONTRAST1.8 1.2 0.8 9.4 10 10 EXAMPLE 18 CONTRAST 1.8 1.3 0.9 9.0 10 10 EXAMPLE19 CONTRAST 1.8 1.4 0.8 8.9 10 10 EXAMPLE 20 CONTRAST 1.8 1.5 0.6 8.6 1010 EXAMPLE 21 CONTRAST 1.8 1.6 1.1 7.9 10 10 EXAMPLE 22 CONTRAST 1.8 1.71.1 8.0 10 10 EXAMPLE 23 CONTRAST 1.8 1.8 1.6 8.3 10 10 EXAMPLE 24EXAMPLE 19 1.8 1.9 1.3 1.8 10 10 EXAMPLE 20 1.8 2.0 1.7 1.5 10 10

TABLE 5 RELATIONSHIP BETWEEN YOUNG MODULES OF MAGNETIC DISC MEDIUMPROTECTIVE LAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHTWEAR THICKNESS YOUNG YOUNG HEIGHT OF WEAR OF THICKNESS MODULES OFMODULES OF MAGNETIC HEIGHT OF MAGNETIC OF MAGNETIC MAGNETIC DISCMAGNETIC DISC MAGNETIC DISC MEDIUM HEAD MEDIUM HEAD MEDIUM HEADPROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE LAYERLAYER LAYER LAYER LAYER LAYER NO. (GPa) (GPa) (nm) (nm) (nm) (nm)CONTRAST 200 150 0.4 8.6 10 10 EXAMPLE 25 CONTRAST 200 200 0.8 8.9 10 10EXAMPLE 26 EXAMPLE 21 200 250 1.2 1.6 10 10 EXAMPLE 22 200 300 1.1 1.810 10 EXAMPLE 23 200 350 1.0 1.1 10 10 EXAMPLE 24 200 400 1.5 0.8 10 10EXAMPLE 25 200 450 1.6 0.9 10 10 EXAMPLE 26 200 500 1.7 0.5 10 10

TABLE 6 RELATIONSHIP BETWEEN YOUNG MODULES OF MAGNETIC DISC MEDIUMPROTECTIVE LAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHTWEAR THICKNESS YOUNG YOUNG HEIGHT OF WEAR OF MODULES OF MODULES OFMAGNETIC HEIGHT OF MAGNETIC THICKNESS MAGNETIC MAGNETIC DISC MAGNETICDISC OF MAGNETIC DISC MEDIUM HEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVEPROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE LAYER LAYER LAYERLAYER LAYER LAYER NO. (GPa) (GPa) (nm) (nm) (nm) (nm) CONTRAST 300 1500.8 9.7 10 10 EXAMPLE 27 CONTRAST 300 200 1.1 8.6 10 10 EXAMPLE 28CONTRAST 300 250 0.9 8.5 10 10 EXAMPLE 29 CONTRAST 300 300 1.5 7.8 10 10EXAMPLE 30 EXAMPLE 27 300 350 1.1 1.4 10 10 EXAMPLE 28 300 400 1.5 1.010 10 EXAMPLE 29 300 450 1.6 1.1 10 10 EXAMPLE 30 300 500 1.4 0.8 10 10CONTRAST 400 150 0.6 9.4 10 10 EXAMPLE 31 CONTRAST 400 200 0.6 9.8 10 10EXAMPLE 32 CONTRAST 400 250 0.7 9.3 10 10 EXAMPLE 33 CONTRAST 400 3000.8 9.6 10 10 EXAMPLE 34 CONTRAST 400 350 1.0 9.0 10 10 EXAMPLE 35CONTRAST 400 400 1.5 8.4 10 10 EXAMPLE 36 EXAMPLE 31 400 450 1.2 1.5 1010 EXAMPLE 32 400 500 1.5 1.0 10 10

TABLE 7 RELATIONSHIP BETWEEN HARDNESS OF MAGNETIC DISC MEDIUM PROTECTIVELAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHT WEAR THICKNESSHARDNESS HEIGHT OF WEAR OF HARDNESS OF OF MAGNETIC HEIGHT OF MAGNETICTHICKNESS MAGNETIC MAGNETIC DISC MAGNETIC DISC OF MAGNETIC DISC MEDIUMHEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVEPROTECTIVE PROTECTIVE LAYER LAYER LAYER LAYER LAYER LAYER NO. (GPa)(GPa) (nm) (nm) (nm) (nm) CONTRAST 40 40 0.4 8.6 1 10 EXAMPLE 37CONTRAST 40 50 0.4 8.1 1 10 EXAMPLE 38 EXAMPLE 33 40 60 0.3 1.1 1 10EXAMPLE 34 40 70 0.1 1.0 1 10 EXAMPLE 35 40 75 0.3 1.2 1 10 CONTRAST 4080 1.0 9.1 1 10 EXAMPLE 39 CONTRAST 40 90 1.0 9.2 1 10 EXAMPLE 40CONTRAST 40 100 1.0 9.8 1 10 EXAMPLE 41 CONTRAST 40 110 1.0 9.6 1 10EXAMPLE 42 CONTRAST 40 120 1.0 9.0 1 10 EXAMPLE 43 CONTRAST 40 130 1.08.8 1 10 EXAMPLE 44 CONTRAST 40 140 1.0 8.7 1 10 EXAMPLE 45

TABLE 8 RELATIONSHIP BETWEEN HARDNESS OF MAGNETIC DISC MEDIUM PROTECTIVELAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHT WEAR THICKNESSHARDNESS HEIGHT OF WEAR OF HARDNESS OF OF MAGNETIC HEIGHT OF MAGNETICTHICKNESS MAGNETIC MAGNETIC DISC MAGNETIC DISC OF MAGNETIC DISC MEDIUMHEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVEPROTECTIVE PROTECTIVE LAYER LAYER LAYER LAYER LAYER LAYER NO. (GPa)(GPa) (nm) (nm) (nm) (nm) CONTRAST 40 40 0.2 9.1 5 10 EXAMPLE 46CONTRAST 40 50 0.3 8.2 5 10 EXAMPLE 47 EXAMPLE 36 40 60 0.1 1.4 5 10EXAMPLE 37 40 70 0.1 1.2 5 10 EXAMPLE 38 40 75 0.2 1.6 5 10 CONTRAST 4080 5.0 4.6 5 10 EXAMPLE 48 CONTRAST 40 90 5.0 8.4 5 10 EXAMPLE 49CONTRAST 40 100 5.0 7.9 5 10 EXAMPLE 50 CONTRAST 40 110 5.0 9.1 5 10EXAMPLE 51 CONTRAST 40 120 5.0 9.2 5 10 EXAMPLE 52 CONTRAST 40 130 5.09.4 5 10 EXAMPLE 53 CONTRAST 40 140 5.0 8.5 5 10 EXAMPLE 54

TABLE 9 RELATIONSHIP BETWEEN HARDNESS OF MAGNETIC DISC MEDIUM PROTECTIVELAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHT WEAR THICKNESSHARDNESS HEIGHT OF WEAR OF HARDNESS OF OF MAGNETIC HEIGHT OF MAGNETICTHICKNESS MAGNETIC MAGNETIC DISC MAGNETIC DISC OF MAGNETIC DISC MEDIUMHEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVEPROTECTIVE PROTECTIVE LAYER LAYER LAYER LAYER LAYER LAYER NO. (GPa)(GPa) (nm) (nm) (nm) (nm) CONTRAST 40 40 0.1 9.3 10 10 EXAMPLE 55CONTRAST 40 50 0.2 9.4 10 10 EXAMPLE 56 EXAMPLE 39 40 60 0.1 1.0 10 10EXAMPLE 40 40 70 0.2 1.3 10 10 EXAMPLE 41 40 75 0.1 1.2 10 10 CONTRAST40 80 10.0 7.6 10 10 EXAMPLE 57 CONTRAST 40 90 10.0 8.5 10 10 EXAMPLE 58CONTRAST 40 100 10.0 8.6 10 10 EXAMPLE 59 CONTRAST 40 110 10.0 9.6 10 10EXAMPLE 60 CONTRAST 40 120 10.0 8.9 10 10 EXAMPLE 61 CONTRAST 40 13010.0 9.3 10 10 EXAMPLE 62 CONTRAST 40 140 10.0 9.1 10 10 EXAMPLE 63

TABLE 10 RELATIONSHIP BETWEEN HARDNESS OF MAGNETIC DISC MEDIUMPROTECTIVE LAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHTWEAR THICKNESS HARDNESS HEIGHT OF WEAR OF HARDNESS OF OF MAGNETIC HEIGHTOF MAGNETIC THICKNESS MAGNETIC MAGNETIC DISC MAGNETIC DISC OF MAGNETICDISC MEDIUM HEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVE PROTECTIVEPROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE LAYER LAYER LAYER LAYERLAYER LAYER NO. (GPa) (GPa) (nm) (nm) (nm) (nm) CONTRAST 40 40 0.2 8.615 10 EXAMPLE 64 CONTRAST 40 50 0.3 9.2 15 10 EXAMPLE 65 CONTRAST 40 600.1 5.6 15 10 EXAMPLE 66 CONTRAST 40 70 0.2 4.2 15 10 EXAMPLE 67CONTRAST 40 75 0.1 2.3 15 10 EXAMPLE 68 CONTRAST 40 80 1.3 1.0 15 10EXAMPLE 69 CONTRAST 40 90 1.9 1.3 15 10 EXAMPLE 70 CONTRAST 40 100 1.51.3 15 10 EXAMPLE 71 CONTRAST 40 110 1.3 1.2 15 10 EXAMPLE 72 CONTRAST40 120 0.2 0.2 15 10 EXAMPLE 73 CONTRAST 40 130 0.1 0.2 15 10 EXAMPLE 74CONTRAST 40 140 0.2 0.1 15 10 EXAMPLE 75

TABLE 11 RELATIONSHIP BETWEEN HARDNESS OF MAGNETIC DISC MEDIUMPROTECTIVE LAYER AND MAGNETIC HEAD PROTECTIVE LAYER, AND WEAR HEIGHTWEAR THICKNESS HARDNESS HEIGHT OF WEAR OF HARDNESS OF OF MAGNETIC HEIGHTOF MAGNETIC THICKNESS MAGNETIC MAGNETIC DISC MAGNETIC DISC OF MAGNETICDISC MEDIUM HEAD MEDIUM HEAD MEDIUM HEAD PROTECTIVE PROTECTIVEPROTECTIVE PROTECTIVE PROTECTIVE PROTECTIVE LAYER LAYER LAYER LAYERLAYER LAYER NO. (GPa) (GPa) (nm) (nm) (nm) (nm) CONTRAST 40 40 0.1 9.220 10 EXAMPLE 76 CONTRAST 40 50 0.2 8.2 20 10 EXAMPLE 77 CONTRAST 40 600.3 5.3 20 10 EXAMPLE 78 CONTRAST 40 70 0.3 4.3 20 10 EXAMPLE 79CONTRAST 40 75 1.3 5.3 20 10 EXAMPLE 80 CONTRAST 40 80 1.0 1.2 20 10EXAMPLE 81 CONTRAST 40 90 1.2 1.3 20 10 EXAMPLE 82 CONTRAST 40 100  1.31.1 20 10 EXAMPLE 83 CONTRAST 40 110  1.3 1.0 20 10 EXAMPLE 84 CONTRAST40 120  0.2 0.2 20 10 EXAMPLE 85 CONTRAST 40 130  0.1 0.2 20 10 EXAMPLE86 CONTRAST 40 140  0.1 0.1 20 10 EXAMPLE 87

What is claimed is:
 1. A magnetic disc apparatus comprising a magneticdisc medium having a protective layer of thickness between 1 and 10 nmon the surface, a means for rotating the magnetic disc medium, amagnetic head for recording and reproducing data on and from themagnetic disc medium, and a control means for controlling the magneticdisc medium, the rotating means and the head, wherein the head has aprotective layer formed on at least part of a portion to be infrictional contact with the magnetic disc medium, the magnetic headprotective layer of a hardness between 1.5 and 2.0 times the hardness ofthe magnetic disc medium protective layer.
 2. The magnetic discapparatus according to claim 1, wherein the magnetic head protectivelayer and the magnetic disc medium protective layer are made of the samematerial.
 3. The magnetic disc apparatus according to claim 1, whereinthe magnetic head protective layer and the magnetic disc mediumprotective layer are made of material including mainly carbon.
 4. Amagnetic disc apparatus comprising a magnetic disc medium having aprotective layer on its surface, and a magnetic head for recording andreproducing data on and from the magnetic disc medium having aprotective layer on its surface, the magnetic disc medium and themagnetic head being rotated in frictional contact therebetween, whereinthe magnetic head protective layer has a Young's modulus higher than theYoung's modulus of the magnetic disc medium protective layer, whereinthe Young's moduluses of the magnetic disc medium protective layer andthe magnetic head protective layer are set to be in range of 200 to 400(GPa) and 250 to 500 (GPa), respectively.
 5. The magnetic disc apparatusaccording to claim 4, wherein the magnetic head protective layer and themagnetic disc medium protective layer are formed as a carbon layer withor without a hydrogen or nitrogen content.
 6. The magnetic discapparatus according to claim 4, wherein the magnetic head protectivelayer and the magnetic disc medium protective layer are formed as SiC,SiN or BN.
 7. A magnetic disc apparatus comprising: a magnetic discmedium having a protective layer on its surface; and a magnetic headalso having a protective layer on its surface, said magnetic head forrecording and reproducing data on and from the magnetic disc medium, themagnetic disc medium and the magnetic head being rotated in frictionalcontact therebetween, wherein a thickness of the magnetic disc mediumprotective layer is set to be between 1 and 10 nm, and a hardness of themagnetic bead protective layer is set to be between 1.5 and 2.0 times ahardness of the magnetic disc medium protective layer.
 8. The magneticdisc apparatus according to claim 7, wherein the magnetic headprotective layer and the magnetic disc medium protective layer areformed as a carbon layer with or without a hydrogen or nitrogen content.9. The magnetic disc apparatus according to claim 7, wherein themagnetic head protective layer and the magnetic disc medium protectivelayer are formed as SiC, SiN or BN.